A screen material having a flexible member. The screen material includes closely spaced filter wires supported by a plurality of support members. A stranded cable is used as the support members to provide flexibility to the screen material. The filter wires are welded to the members and define filter gaps between adjacent filter wires to allow liquid and small particles to pass through, while retaining particles too large to fit through the filter gaps.

Well screen assembly for use in horizontal wells and other situations where tensile, torsion and bending forces can damage well screens which are welded to their end supports provides a floating mounting which eliminates welding of the screen segments. A pair of complementary inner and outer slip rings are provided at one end of the well screen assembly with the inner ring being in sealed relationship with a screen segment and the outer ring being integrally affixed to an outer protective cover member and an axial support member such as a pipe base member or a tubular end fitting. The inner ring is free to slide and rotate relative to the outer ring.

Well casing assembly for use in oil and gas wells, and especially deviated or horizontal wells, has an inner pipe member with threaded ends which permit a number of casing assemblies to be joined in a string. The inner pipe has a series of perforations along a segment of its length which are covered by an elongated screen member which prevents the passage of sand particles. A concentric outer protective cover member is devoid of perforations in regions which are radially opposite the inner screen to prevent damage to the screen. One or more perforated segments of the outer member are axially spaced from the screen member so that inward flow from a formation will have its energy and velocity reduced before it reaches the screen, thereby minimizing erosion of the screen surface. If desired, perforated flow control devices such as annular rings can be located between the inner pipe and outer member at the ends of the screen segment to allow a more uniform flow to the screen, and thus further reduce erosion.

An apparatus for treating water includes a vertically extending contact vessel, wherein water is contacted with ozone, and a return vessel which contains a column of water of a sufficient height to drive water through downstream solids separation stages. Ozone is removed from the water and the rate of ozone injection is monitored and automatically adjusted so that no great amount of ozone remains in water entering the solids separation stages. The ozone is generated in elongated elements that are cooled by the process water and that are positioned to serve as a static mixer for such water.

Lateral member assembly for use in an underdrain lateral distribution system is made of plastics but is as capable as much heavier and more costly prior art metallic assemblies in supporting a bed of filter media which must be periodically backwashed with liquid and gas. Complementary elements, including a rigid extruded floor plate member having longitudinally extending side edge channels, and an overlying screen member having flange portions adapted to be retained by undercut recesses in the side edge channels, are adapted to be assembled to each other to form hollow lateral assemblies. In a preferred embodiment, the screen member is telescopically assembled to the floor plate member to cause the screen flange portions to interlock with the recesses in the side edge channels. The resulting assembly is sealed against leakage where the members are interlocked by a pair of flexible, integral plastic sealing strips which are co-extruded with the rigid floor plate member. In an alternative arrangement, the flange portions of the screen members engage a cam surface on the floor plate member which forces them away from each other as the screen member is pressed down against the floor plate member, thus causing them to snap into the undercut recesses in the side edge channels. The flange portions are then retained in a locked relationship with the floorplate member and sealed by flexible rod members forced into the space between the outside surfaces of the screen member and the outer walls of the side edge channels.